Spinning rotors are subject to extensive wear of the surfaces which come into contact with the textile fibers being spun or the resultant spun yarn. It is known to apply a coating having hard material granules embedded therein to the surface of the spinning rotor to increase the wear resistance of the rotor surface. A representative form of such a coating is a nickel-diamond coating, for example. It is intended to also achieve a good spinning performance of the spinning rotor by means of the nickel-diamond coating, besides good wear properties.
Coatings with embedded hard material granules are known in a variety of embodiments. German Patent Publication DE 197 13 359 A1, for example, describes a spinning rotor with a rotor cup, whose inner surface has a nickel dispersion layer of uniform layer thickness, wherein the concentration of the hard material granules embedded in the nickel dispersion layer is clearly less on the fiber slide face in the area of the surface of the nickel dispersion layer than in the rotor groove.
With the spinning rotor for open-end spinning units represented in German Patent Publication DE 198 25 906 A1, the fiber collection groove is provided with a nickel-diamond coating, and the fiber slide face with a coating of pure nickel. The coatings are applied in separate coating operations and separate baths. In the course of this coating operation, the entire inner and outer contours of the rotor disk are initially provided with a nickel coating, although from the viewpoint of function it is only required on the fiber slide face. In this manner, the nickel coating provides corrosion protection of the remaining surfaces. The nickel-diamond coating is thereafter applied to the nickel coating only in the fiber collection groove.
German Patent Publication DE 198 22 265 A1discloses an open-end spinning rotor with a fiber slide face provided with a nickel-diamond coating. This nickel-diamond coating consists of an inner support layer and an outer working layer. In this case, the diamond granules embedded in the inner support layer are larger than the diamond granules embedded in the outer working layer. The support layer and the working layer are interlocked.
In addition to the wear caused by the fiber material, the surface at the interior of the spinning rotor can be subjected to mechanical, intermittently occurring stress during the cleaning process. Cleaning of the rotor interior is performed in case of a malfunction report triggered by soiling of the spinning rotor, or as a part of the piecing process. Various processes for cleaning rotors are known. The rotor surface is stressed to a greater or lesser degree, depending on the intensity of cleaning. Since normally the complete cleaning of the spinning rotor is desired, intensive cleaning processes are preferred. In many cases, blowing compressed air through the spinning rotor is not sufficient by itself, since shell particles can become jammed in the narrow rotor grooves. Dependable cleaning is assured if the spinning box is flipped open and the spinning rotor is worked by means of suitable instruments. In the course of a customary intensive cleaning process to remove or avoid the interference with the spinning quality or with piecing, the dirt on the inside of the spinning rotor, in particular in the rotor groove, is loosened by means of a scraper and removed from the rotor by compressed air. The scraper customarily also consists of a wear- resistant material, for example fiberglass-reinforced plastic or hardened material, such as steel. Pieces can be broken out of the above-described rotor coating because of the stress which is exerted by the scraper on the coated surface. Breaking or flaking off of the coating occurs in an uncontrolled manner. The separated pieces can be large enough so that the base material of the spinning rotor is exposed. As a result, the wear protection by means of the nickel-diamond coating is completely interrupted in places. These places can promote the breaking off of further adjoining pieces of the known coating down to the base material.
Flaking or breaking off of pieces of the coating can also be triggered by the oscillations occurring at the rotor.
Pieces of the coating used for wear protection down to the base material can flake off from all known nickel-diamond coatings. The service life of the spinning rotor is clearly reduced by this damage.